Enhanced Oil Recovery (EOR) may be used to increase oil recovery in oil fields worldwide. One type of EOR process utilizes one or more chemical solvents to enhance oil recovery from an oil-bearing formation. The chemical solvent is selected to be soluble or miscible with oil in the formation and to have a lower viscosity than the oil in the formation so that the viscosity of the oil in the formation is reduced upon mixing with the solvent. The solvent is injected into the formation to mix with the oil, reducing the viscosity of the oil and mobilizing the oil for production from the formation. Chemical solvent EOR processes may boost the oil recovery factor from an oil-bearing formation and may extend the oil-producing life of the formation.
Dimethyl ether (DME) has been disclosed as a chemical solvent for use in EOR processes to recover oil from subterranean oil-bearing formations. When DME is used as an EOR agent, DME is produced from the formation in a mixture with oil and water or brine. The DME must be separated from the oil phase of the produced mixture to provide a DME uncontaminated oil for refining, where the DME uncontaminated oil may contain only minute quantities of DME.
Separation of DME from oil to produce DME uncontaminated oil, however, has proven difficult. A portion of the DME may be separated from the oil phase of a produced mixture of DME, oil, and water or brine by using a degasser to reduce the Reid Vapor Pressure of the oil phase. In the degasser, the oil phase is heated and flashed to separate volatile DME from the less volatile components of the oil phase. However, this process only removes a maximum of 50% of the DME from the oil—which is insufficient to provide an oil uncontaminated with DME for refining.
What is needed is a system and a process for separating DME from a mixture of DME, oil, and water or brine, where substantially all of the DME may be separated from the oil phase of the mixture. When DME is used as an EOR agent to promote recovery of oil from an oil-bearing formation, what is further needed is a system and a process in which substantially all of the DME may be recovered from a mixture of DME, oil, and water or brine produced from the formation for reintroduction into the formation.